The U.S. Marshals Service has flown in about a dozen deputies from the mainland to provide 24-hour protection to the federal judge whose order blocked the president's travel ban from taking effect.

U.S. District Judge Derrick Watson has received death threats after he issued a ruling last week.

Meanwhile, the FBI is also aware of the threats and are prepared to assist the U.S. Marshals Service if needed.

The FBI would not comment further on how the threats were made.

The agency would also not provide details on what states the threats are coming out of. However, sources say, they are coming from the mainland.

Former federal agent Tommy Aiu said it's not unusual for additional deputies to be brought in to help the local U.S. Marshals office with protection needs.

"The U.S. Marshals service will do a critical risk assessment, look at the threat, make an analysis, and determine the level of protection needed," he said.

Watson issued the order last Wednesday to temporarily block enforcement of the ban, just hours before it was to take effect. The ban would have frozen immigration from six predominantly Muslim countries for 90 days.

Watson's ruling thrust Hawaii into the center of a polarizing debate over immigration reform, which have spurred protests for and against the ban.

The U.S. Marshals Service refused to comment on security details so it's unknown how long the extra protection will continue.